This disease, which affects both upper and lower airways, can be spread by contact through nasal secretions and aerosol inhalation.

"We are excited to offer a safe vaccine option for veterinarians and horse owners," said John Tuttle, DVM, senior associate director of equine professional and technical services. "As a worldwide leader in equine health-care solutions, we also have an obligation to help educate the industry about the prevalence, diagnosis and treatment of this disease."

Widespread incidence

ERAV has been isolated from Thoroughbred horses with acute respiratory disease in the United States, Canada, Australia, Japan, and Europe, and is emerging as an important disease in these regions. In a recent U.S. study, 73% of all sampled horses less than 3 years old exhibited serum-neutralizing (SN) antibodies to ERAV, and 90% of those 4 or older were positive for the virus.

"Researchers are continuing to learn more about the prevalence of this disease," Tuttle said. "Performance horses that are co-mingled, stabled, entering training, and 1 two 2 years of age or older appear to be at risk."

Early, specific diagnosis is the foundation of effective management of equine respiratory disease. Clinical signs associated with infection with ERAV can include fever, serous (clear) nasal discharge, coughing, abnormal lung sounds, anorexia, pharyngitis (inflammation of the wall of the pharynx), lymphadenitis (Inflammation of one or more lymph nodes), increased tracheal mucus production, and occasionally, leg edema. Infection is accompanied by viremia that develops three to seven days following infection and typically lasts for four to five days, with disappearance of virus from blood coinciding with onset of antibody production. Veterinarians should be careful not to confuse ERAV with rhinopneumonitis caused by equine herpesvirus-1 and 4.

"The role of ERAV in causing acute respiratory disease in horses may be underestimated due to the lack of sensitivity of traditional diagnostic testing," Tuttle said. "The virus can be detected from horses with acute, respiratory disease using virus isolation, PCR, or paired SN assay testing."

Promising results

The USDA has granted BIVI a conditional license for ERAV vaccine. A conditional license is eligible for consideration when it is demonstrated that there is a need in the field for such a product. The data required for conditional licensure includes demonstration of a reasonable expectation of efficacy, and acceptable safety and purity requirements as fully licensed products. Efficacy and potency test studies are in progress. A conditionally licensed vaccine can be distributed as authorized in each state, and used by, or under the supervision, of veterinarians.

"Obviously, any number of factors can contribute to respiratory diseases in horses, which is why ERAV can be so difficult to diagnose," Tuttle said. "We are committed to helping veterinarians and horse owners understand this disease and learn more about the effectiveness of vaccination."

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